Typically, on a cable transmission plant, there is a mix of video signals (e.g., quadrature amplitude modulation (QAM) signals carrying video and audio frames for providing traditional television services) and data signals (e.g., Data Over Cable Service Interface Specification (DOCSIS) QAM signals providing data-over-cable services). When a customer premise equipment (CPE) device powers up, the CPE device must, in general, first find a frequency through which to receive a downstream signal. In embodiments, the CPE device operates at a greater efficiency when the downstream signal is a data signal (e.g., a downstream DOCSIS QAM signal).
In order to find a downstream data signal, the CPE device needs to distinguish data signals from video signals. CPE devices typically distinguish data signals from video signals by analyzing one or more packet identifiers (PID) associated with the frames carried by the signal. For example, when the CPE device analyzes a PID and identifies the PID as a PID associated with video (e.g., a Moving Picture Experts Group (MPEG) PID), the CPE device can make the determination that the signal is a video signal. However, in order to identify a PID within a signal, the CPE device generally must lock onto the signal (e.g., acquire QAM lock), decode and check parity of the signal through error correction (e.g., acquire forward error correction (FEC) lock), and acquire a lock onto a transmission convergence layer (e.g., MPEG) associated with the signal (e.g., by decoding an MPEG frame within the signal). This process for identifying and analyzing a PID is time-consuming. Therefore, a need exists for improving methods and systems for scanning for and locking onto downstream data signals.
Like reference numbers and designations in the various drawings indicate like elements.